Aerated liquids, such as aerated beverages and the like are typically stored under pressure, in airtight containers or the like, in order to maintain the liquid in an aerated state, or at least reduce the extent to which the gas, whether carbon dioxide or other gas, escapes from the liquid.
Once the container has been opened, the gases tend to discharge from the liquid. The process of discharge can be slowed to a certain extent by resealing the container. However, after resealing, there is typically an enlarged head space available into which the gas can discharge.
It is well known that if the head space can be decreased as the beverage or other liquid volume decreases, so the extent to which gas is discharged or otherwise lost from the liquid may be reduced. To this end, a number of collapsible containers have been provided to date. Some of these collapsible containers have been of the bellows-type. Such containers possess a number of disadvantages.
Primarily, these containers do not function as pressure vessels, so they cannot be used to house soft drink prior to sale. If such a container is filled with soft drink, the internal pressure from the liquid forces the container to over expand after the cap is placed on. The container overstretches into a `blown-out` state allowing a large headspace to develop with resulting loss of carbonation. This would occur with even mild agitation, and the container could never be expected to withstand the rigours of transportation and handling methods expected of a soft drink vessel leaving the bottling plant.
Secondly, this capacity of bellows-type containers to expand as well as collapse means that after the container base been partially collapsed and recapped, it is susceptible to re-expansion and subsequent loss of carbonation as the pressure from the liquid forces a headspace to form, particularly if the container was to be dropped or shaken in any way. This rather defeats the intended purpose.
Though some bellows-type containers possess improvements, they do not fully overcome the abovementioned problems. They must also be manufactured to relatively fine tolerances and are relatively inconvenient to use.
U.S. Pat. No. 4,790,361 (Jones et al) attempted to overcome the problem of over expansion before any collapse is required, after the container is filled. Unfortunately, this can never be achieved in a bellows-type container without some external clamping device to hold it in place. Such a device would have to be joined to the container, resulting in increased expense. While this container might partially resist expansion `beyond full` it would still yield to the very high pressures generated from agitated soft drink.
As such expansion occurs, the intended shape of the Jones et al container would also be `stretched out` of the plastic, resulting in irreparable damage to the polymer. This container would also be virtually impossible to manufacture in the current plastics of choice--polyethylene terephthalate (PET). Also, due to the large surface area of such a container there would be increased expense in material costs. This container would also be susceptible to re-expansion from a collapsed state.
Jones et al has its corrugations defined by a plurality of ridges and grooves, each ridge preferably consisting of planar regions defined by quadrilaterals and acting as a hinge about which the collapsing can take place. U.S. Pat. No. 4,492,313 (Touzani) also does not function initially as a pressure vessel. It, too, cannot therefore be used to package soft drink prior to sale. Touzani does go some way in overcoming the problem of re-expansion from a partially collapsed state. The method in which Touzani achieves this introduces other problems however. The container collapses in a somewhat `sectional` manner, and expels the contents in "jumps", which may not match the volume of headspace left. This sectional manner of collapse also results in some of the contents splashing out. Also, the operator can accidentally over compress the container after the cap has been placed on (by folding the rings down), the result of which is some overflow of the contents when the cap is next released.
In British Patent Specification 781, 103 (International Patents Trust) a container for a viscous material such as toothpaste is provided with axial corrugations along its side wall. Pressure on the base enables it to move inwardly of the wall as the wall folds, dispensing the material. In U.S. Pat. No. 4,865,211 (Hollingworth), Netherlands Patent 294186 (Metal Box), U.S. Pat. No. 4,456,134 (Cooper) and French Patents 2294297 (Normos) and 623181 (Leisse) various other collapsible containers are proposed, using a concertina or other folding wall type construction. These containers are not suitable for soft drink however. The containers of U.S. Pat. No. 4,865,211 and UK Patent 781,103 are particularly unsuitable as they are more easily subjected to internal pressure that would over expand them when full as a result of the corrugations and tucks they each employ.
These containers would also re-expand readily from a collapsed state, particularly as they are designed with a flexible material. UK Patent 781,103 is particularly susceptible to re-expansion.
Each of these containers collapses with the fold in a circular or ring shape best illustrated by FIG. 8 in U.S. Pat. No. 4,865,211. Reference is specifically made in NL Patent 294186 and UK Patent 781,103 to the wall folding upon itself or to lie against the uncollapsed circular wall yet to be folded. The walls in these containers are made of a flexible material like polythene. In the case of UK Patent 781,103 the contents are not fluid but are somewhat viscous. This provides support to the container walls under collapsing forces, as the material resists movement therein. This helps the flexible walls to resist buckling under collapsing forces.
Other collapsible containers have included a relatively flexible bag portion which is collapsed to reduce the available headspace. While simple bag-in-the-box collapsible containers can house a liquid like `still` wine, they cannot house beverages under pressure, such as `sparkling` wine. This is due to the propensity a simple bag has to re-expand after collapse if there is pressure within. Improvements to this type of collapsible container have therefore to date concentrated on requiring some separate control means such as an outer container, shell or the like to control collapse and maintain the collapsed container in the collapsed state. The external control device would add considerable cost to the container as it would always have to accompany the bag. Examples of such containers are described in the patents to Cooper and Normos referred to above.
With regard to the bases of PET and other plastics containers, various proposals have been made as to possible designs, one of the most popular at the present time being the "petaloid" base of New Zealand Patent 227274 (Continental Pet Technologies, Inc).
It is an object of at least one embodiment of this invention to come some way in overcoming the problems mentioned above or at least to provide the public with a useful choice.
Other objects of this invention will become apparent from the following description.